On Mon, Oct 10 2022 at 10:41P -0400, Luo Meng <[email protected]> wrote:
> From: Luo Meng <[email protected]> > > If dm_get_device() create dd in multipath_message(), > and then call table_deps() after dm_put_table_device(), > it will lead to concurrency UAF bugs. > > One of the concurrency UAF can be shown as below: > > (USE) | (FREE) > | target_message > | multipath_message > | dm_put_device > | dm_put_table_device # > | kfree(td) # table_device *td > ioctl # DM_TABLE_DEPS_CMD | ... > table_deps | ... > dm_get_live_or_inactive_table | ... > retrieve_dep | ... > list_for_each_entry | ... > deps->dev[count++] = | ... > huge_encode_dev | ... > (dd->dm_dev->bdev->bd_dev) | list_del(&dd->list) > | kfree(dd) # dm_dev_internal > > The root cause of UAF bugs is that find_device() failed in > dm_get_device() and will create dd and refcount set 1, kfree() > in dm_put_table() is not protected. When td, which there are > still pointers point to, is released, the concurrency UAF bug > will happen. > > This patch add a flag to determine whether to create a new dd. > > Fixes: 8215d6ec5fee(dm table: remove unused dm_get_device range parameters) > Signed-off-by: Luo Meng <[email protected]> > --- > drivers/md/dm-mpath.c | 2 +- > drivers/md/dm-table.c | 43 +++++++++++++++++++++-------------- > include/linux/device-mapper.h | 2 ++ > 3 files changed, 29 insertions(+), 18 deletions(-) > > diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c > index 0e325469a252..1f51059520ac 100644 > --- a/drivers/md/dm-mpath.c > +++ b/drivers/md/dm-mpath.c > @@ -2001,7 +2001,7 @@ static int multipath_message(struct dm_target *ti, > unsigned argc, char **argv, > goto out; > } > > - r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev); > + r = __dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev, > false); > if (r) { > DMWARN("message: error getting device %s", > argv[1]); > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c > index d8034ff0cb24..ad18a41f1608 100644 > --- a/drivers/md/dm-table.c > +++ b/drivers/md/dm-table.c > @@ -338,12 +338,8 @@ dev_t dm_get_dev_t(const char *path) > } > EXPORT_SYMBOL_GPL(dm_get_dev_t); > > -/* > - * Add a device to the list, or just increment the usage count if > - * it's already present. > - */ > -int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, > - struct dm_dev **result) > +int __dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, > + struct dm_dev **result, bool create_dd) > { > int r; > dev_t dev; > @@ -367,19 +363,21 @@ int dm_get_device(struct dm_target *ti, const char > *path, fmode_t mode, > > dd = find_device(&t->devices, dev); > if (!dd) { > - dd = kmalloc(sizeof(*dd), GFP_KERNEL); > - if (!dd) > - return -ENOMEM; > - > - if ((r = dm_get_table_device(t->md, dev, mode, &dd->dm_dev))) { > - kfree(dd); > - return r; > - } > + if (create_dd) { > + dd = kmalloc(sizeof(*dd), GFP_KERNEL); > + if (!dd) > + return -ENOMEM; > > - refcount_set(&dd->count, 1); > - list_add(&dd->list, &t->devices); > - goto out; > + if ((r = dm_get_table_device(t->md, dev, mode, > &dd->dm_dev))) { > + kfree(dd); > + return r; > + } > > + refcount_set(&dd->count, 1); > + list_add(&dd->list, &t->devices); > + goto out; > + } else > + return -ENODEV; > } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) { > r = upgrade_mode(dd, mode, t->md); > if (r) > @@ -390,6 +388,17 @@ int dm_get_device(struct dm_target *ti, const char > *path, fmode_t mode, > *result = dd->dm_dev; > return 0; > } > +EXPORT_SYMBOL(__dm_get_device); > + > +/* > + * Add a device to the list, or just increment the usage count if > + * it's already present. > + */ > +int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, > + struct dm_dev **result) > +{ > + return __dm_get_device(ti, path, mode, result, true); > +} > EXPORT_SYMBOL(dm_get_device); > > static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev, > diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h > index 04c6acf7faaa..ef4031a844b6 100644 > --- a/include/linux/device-mapper.h > +++ b/include/linux/device-mapper.h > @@ -178,6 +178,8 @@ dev_t dm_get_dev_t(const char *path); > int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, > struct dm_dev **result); > void dm_put_device(struct dm_target *ti, struct dm_dev *d); > +int __dm_get_device(struct dm_target *ti, const char *path, fmode_t mode, > + struct dm_dev **result, bool create_dd); > > /* > * Information about a target type > -- > 2.31.1 > This patch is treating the one multipath case like it is only consumer of dm_get_device() that might have this issue. It feels too focused on an instance where dm_get_device()'s side-effect of creating the device is unwelcome. Feels like you're treating the symptom rather than the problem (e.g. that the "kfree() in dm_put_table() is not protected"?) Mike -- dm-devel mailing list [email protected] https://listman.redhat.com/mailman/listinfo/dm-devel
